Watch Dog Timer!

for debugging purposes, I recommend that you make a macro e.g. KICK_THE_PUPPY so that you can enable the watchdog for non-debug and disable it for debug in one place (the first 'kick' enables the wd forever). A simple way to test the WD functioning during development is just to start kicking it and it must then time out.

Erik

Erik, do you know where can I find samples of this function. On how to use the WDT.
I am working on the "KICK_THE_PUPPY".
Thank you

do you know where can I find samples of this function. Not a function, make a macro of the two writes (see datasheet).

Erik

Erik, this is what I did. I do not understand what is going on here. cacn you explain. I am sorry, but this is more complicated than I thought. I opened the WDT peripheral, but all I see is numbers running and running. Help.

#include <Reg932.h>
#include <stdio.h>


void init(void);
void brkrst_init(void);
void Kick_the_Puppy(void);

void Main(void)
{
init();
brkrst_init();
Kick_the_Puppy();

}

void init(void)
{
P1M1 = 0x00; // Quasi-bidirectional
P1M2 = 0x00;
P2M1 = 0x00; // push pull output
P2M2 = 0xFF;
P0M1 = 0x00;
P0M2 = 0xFF; //Output
ES = 1; // enable UART interrupt
EA = 1;
}

void brkrst_init(void) // This function allows ISP entry through the UART break detect
{
//AUXR1 |= 0x40; // enable reset on break detect, pg. 102
SCON = 0x50; // select the BRG as UART baud rate source, pg. 60
SSTAT = 0x00; //Timer1
BRGR0 = 0x70; // 9600 BAUD at @ 7.373MHz internal RC oscillator
BRGR1 = 0x04;
BRGCON = 0x03; // enable BRG, pg. 59
}

void Kick_the_Puppy(void)
{
EA = 0;
WDCON = 0x05; //start WDT, and select WD oscillator
WDL = 0xFF;
WFEED1 = 0x0A5; //feed sequence
WFEED2 = 0x05A;
EA = 1;
while(1);
}

Only the a5/5a load is required to keep the watchdog alive
so the code should be

#define KICK_THE_PUPPY WFEED1 = 0x0A5;        WFEED2 = 0x05A;

void Initialize_the_Puppy(void)
{
EA = 0;
WDCON = 0x05; //start WDT, and select WD oscillator
WDL = 0xFF;
KICK_THE_PUPPY
EA = 1;
while(1); // for test
}

I have no Idea how to find out if it does reset? uhmm...what about an LED lighting after a reset? if this is a good idea, where in the code should I place that instruction...sorry, but I have no idea, but I want to learn this please.
Thank you

there is/are a/some bit(s) for "reset cause"
read up on therm and you will know how

Erik

Are you talking about the Reset Pin Enable (RPE) bit or the R_EX (external reset flag)?

Thank you

I am willing to help, but do not have the time to read the datasheet for you

Erik

Erik, I had to go way from this question, because as you have seen I have to take care of other parts of my program like the external interrupt.
To see if the WDT resets (i guess (meaning it is working fine)) could I cause a software reset? what about if it does not work fine...how do I do that.
There is register called AUXR1 which has a bit for sotfware reset. This will be a good way to know if the WDT is reseting! or do you have a better idea.
Thank you!

There is register called AUXR1 which has a bit for sotfware reset
The bit is a bit more intricate than that. You must toggle it after a cold reset to get any use out of it.

Erik

PS in 'standard 51 language' AUXR1 is not not a register, it is a SFR.

I will toggle the SFR AUXR1. But do you think it will be a good exercise...?
Let me just make sure...if the WDT resets (works fine) then a software reset should happens by if I set up AUXR1 correctly...right?
Then toggle that pin. And this should repit.
Right?
Thanks

then a software reset should happens by if I set up AUXR1 correctly
No, the bit - not "pin" - indicates that a sw reset took place, ir does not make it happen.

If you just want to test the watchdog insert a while(); temporarily.

Erik

OK, Erik I will do this today and let you know thank you. I still have not resolved my problem with the external interrupt and Power Down, but that will be a different question at a different time.

Erik below is the program I am using to test the WDT. I run it by using only the simulator and it worked fine (I think). This is the sample program "blinky" where port 2 shifts from right to left and left to right. The way I have it here is as follows: as soon as it finishes shifting from right to left, it initializes the WDT and after an overflow, occurs it resets the program.
I am still a bit confused. What about in my real application when should I called or initialized the WDT.
For what I understand the WDT should always overflow. If it does not (underflowing) then it means a software error while executing occured. therefore, the WDT will cause an system reset. Right?
How can I keep a count of WDT underflowing... is there an interrupt for it, or just when it is used as a timer. If so what else should be included there. I have never worked with WDT before so this is new to me.

Thanks for your help.

#include <Reg932.h>
#include <stdio.h>
#include <String.h>
UCFG1 = 0x88;

void init(void);
void brkrst_init(void);
void Initialize_the_Puppy(void);
#define KICK_THE_PUPPY WFEED1 = 0x0A5; WFEED2 = 0x05A;
void delay (unsigned int cnt)
{
while (--cnt);
}

void Main(void)
{
brkrst_init();
{
unsigned char i;
P2M1 = 0;
for(;;)
{
for (i = 0x01; i; i <<= 1)
{ P2 = i; // simulate running lights
delay (50000);
}
Initialize_the_Puppy();
for (i = 0x80; i; i >>= 1)
{ P2 = i;
delay (50000);
}

}
}
}

void brkrst_init(void) // This function allows ISP entry through the UART break detect
{
//AUXR1 |= 0x40; // enable reset on break detect, pg. 102
SCON = 0x50; // select the BRG as UART baud rate source, pg. 60
SSTAT = 0x00; //Timer1
BRGR0 = 0x70; // 9600 BAUD at @ 7.373MHz internal RC oscillator
BRGR1 = 0x04;
BRGCON = 0x03; // enable BRG, pg. 59
}

void Initialize_the_Puppy(void)
{
EA = 0;
WDCON = 0x05; //start WDT, and select WD oscillator
WDL = 0xFF;
KICK_THE_PUPPY
EA = 1;
AUXR1 = 0x08;
AUXR1 ^= ~0x08;
while(1); // for test
}